The present disclosure relates generally to medical devices. More specifically, the present disclosure relates to the electrical insulation of medical devices.
Hemodialysis (“HD”) in general uses diffusion to remove waste products from a patient's blood. A diffusive gradient that occurs across the semi-permeable dialyzer between the blood and an electrolyte solution called dialysis fluid causes diffusion. Hemofiltration (“HF”) is an alternative renal replacement therapy that relies on a convective transport of toxins from the patient's blood. This therapy is accomplished by adding substitution fluid to the extracorporeal circuit during treatment (typically ten to ninety liters of such fluid). The substitution fluid and the fluid accumulated by the patient in between treatments is ultrafiltered over the course of the HF treatment, providing a convective transport mechanism, which is particularly beneficial in removing middle and large molecules (in hemodialysis there is a small amount of waste removed along with the fluid gained between dialysis sessions, however, the solute drag from the removal of that ultrafiltrate is typically not enough to provide convective clearance).
Hemodiafiltration (“HDF”) is a treatment modality that combines convective and diffusive clearances. HDF flows dialysis fluid from the dialyzer inlet to its outlet. In addition, substitution fluid is provided directly to the extracorporeal circuit, providing convective clearance. These modalities are administered by a dialysis machine. The machines may be provided in a center or in a patient's home. Dialysis machines provided in a center are used multiple times a day for multiple patients and therefore must be cleaned between treatments. Dialysis machines use multiple components, including electrical components. Electrical components pose a risk for an electrical failure. To safeguard the patient against an internal failure of the dialysis machine's flow path, today's dialyze machines are electrically grounded. Nevertheless, the patient may come in to contact with a device that is not properly grounded, such as chargers for mobile phones or laptop, electrical adjustable chairs, or even reading lamps.
Medical devices are designated into different electrical categories. Cardiac Floating “CF” machines, for example, are machines having components (“applied parts”), which come into direct conductive contact with the patient's heart. Examples of CF machines are heart lung machines, external pacemakers, electrical surgery devices, pacemakers, and defribulators. Body Floating “BF” machines have applied parts that come into conductive contact with the patient, or have medium or long term contact with the patient. Examples of BF machines include monitors, incubators and ultrasound equipment. Body (“B”) machines have applied parts that are normally not conductive and may be immediately released from the patient. Examples of B machines include light emitting diode (“LED”) lighting, medical lasers, MRI body scanners, hospital beds and photography equipment.
CF and BF applied parts have floating patient grounds, while B machines may be connected to earth ground. It is desirable to have a reliable and cost effective way for dialysis machines to maintain a floating patient ground, which can at least approach a BF or CF rated machine.